In the remainder of the document, we will consider that the impact-absorbing system of a motor vehicle comprises vehicle parts capable of absorbing the energy during an impact, in particular during a high speed impact. The absorbing system may therefore comprise a transverse beam supported by the ends of the side members of the vehicle body in white via impact absorbers called “crash boxes”. Note that in this case, the side members are part of the impact-absorbing system. It is reminded that the “body in white” of the vehicle is a structural assembly of this vehicle comprising a chassis, side members and the side vertical members of the vehicle doors.
In case of impact, the transverse beam may work in flexion, if the impact is between the two side members, or without flexion if the beam is too rigid or if the impact occurs at a side member. In all cases, the absorbers are stressed and deform, absorbing as much of the energy of the impact as possible to spare the side members and so that the vehicle can be repaired without repairs to the body in white. This type of traditional impact absorption structure, based on the side members of the body in white, is known as the “upper absorption structure”.
This type of upper structure deals with head-on collisions at high speed (56 to 64 km/h) and insurance impacts. It is reminded that an “High speed” impact correspond to an impact of the vehicle against a rigid or deformable obstacle at a speed of 56 to 64 km/h, dealt with for the purpose of protecting occupants of the vehicle. Furthermore, “insurance impacts” are impacts at about 15 km/h against a rigid wall, such as so-called Danner impacts, or “AZT” impacts, or at about 8 km/h against a pole (IIHS standard pole impact). Such a shock is dealt with for the purpose of reducing the vehicle repair costs and in particular of protecting the body in white of the vehicle.
In addition to an upper absorption structure, some vehicles also have a “lower absorption structure”, leaning on extensions of the engine cradle or on small side members substantially parallel to the side members of the upper absorption structure but located at the height of a pedestrian impact beam. An engine cradle comprising extensions is called “long cradle”, as opposed to an engine cradle without extensions, known as “short cradle”.
If a motor vehicle is equipped with a lower structure, it also has a second lower structure transverse beam and possibly an absorber supported by this second transverse beam. This lower structure can deal with both pedestrian impacts and insurance impacts. “Pedestrian impacts” on bumpers correspond to a shock of an impactor simulating the leg of a pedestrian striking the bumper at 40 km/h.
This type of lower structure distributes the energy to be absorbed in case of impact between this lower structure and the traditional upper structure through the side members. Especially in case of insurance impact, roughly ⅔ of the energy is absorbed by the upper structure and ⅓ by the lower structure.
Nevertheless, some vehicles do not have cradle extensions to form a lower structure in addition to the upper structure at the height of the side members. In this case, longer impact absorbers are generally required on the upper structure, in order to absorb sufficient energy in case of insurance impact. To accommodate these longer absorbers, the overhang in the longitudinal direction of the vehicle, in other words the length of the front part of this vehicle between the side members and the bumper skin, must be increased.